BRIEF DESCRIPTION OF THE PRIOR ART
It is known in surgery to use certain types of electrical devices for resectioning organs of the human body in a way such that the resectioning procedure is virtually hemostatic in character, or to use a cauterizing or coagulating-type current application following a procedure involving surgical cutting, so as to thereby reduce the risk of excessive trauma or injury from hemorrhaging to a minimum.
Patents which have described systems of this type include Falk et al U.S. Pat. No. 4,512,343 which discloses a medical coagulating instrument. This instrument includes an elongated conductive shaft with an insulating jacket. At one end, an insulating handle is provided for manipulation by the surgeon during use. The electrically conductive shaft is insulated by means of a jacket of insulating material which is sleeved onto the shaft. A connector is provided at the proximal end of the shaft to facilitate connection to a high frequency current source.
The insulating sleeve placed on the shaft can desirably include a plurality of individual plastic conduit pieces which are individually injected molded and dimensioned to slip over the shaft with a close fit providing abutting end faces which engage each other to form a substantially continuous sleeve. A second insulating sleeve can be placed over that which is next to the shaft by providing a heat-shrink plastic material on the outer side of the initial sleeve.
Taylor U.S. Pat. No. 4,534,347 discloses a microwave coagulating scalpel which simultaneously cuts and coagulates. The instrument is particularly useful for resectioning highly vascular tissue. The scalpel blade forms both a cutting edge and a microwave radiator loop. Organs which can be especially usefully resectioned and coagulated with the instrument described in this patent are the spleen and the liver. In the use of the instrument, the microwave-induced thermal field creates a coagulated crust which rapidly heals following the surgical resectioning. This patentee acknowledges that other types of electrosurgical techniques have been employed using resistance-heated scalpels, radio frequency cutting devices of both the unipolar and bipolartype and plasma scalpels.
The first commercial radio frequency scalpels appeared in 1926 but were not generally accepted by surgeons until the development of non-explosive anesthetics in the late 1950's. Later, in the 1970's, solid state R.F. scalpels were developed and have been widely installed in operating rooms. Cutting and coagulation occur at the tip of a probe electrode where the current is concentrated. After passing through the zone of the flesh to be cut, the current then dissipates and spreads out through the body of the patient to a large "butt plate" upon which the patient rests. Whether the instrument cuts or coagulates is determined by the electrical power and wave form applied to the conductor. Examples of scalpels of this type are disclosed in U.S. Pat. Nos. 3,089,496 and 4,318,409.
In conventional electrosurgery, the cutting of tissue is achieved by an electric current discharge. The region of intense current is of a short path, but heats the tissue intensely, causing the cells to actually burst into steam. The cutting thus occurring is caused by the discharge of an appropriate electrode to the tissue. The sharpened blade forming the electrode does not actually effect mechanical cutting. Desiccation, cauterization or coagulation in conventional electrosurgery are caused by holding the active electrode in polar contact with the tissue. The electric current passes directly into the tissue, thereby causing localized resistance heating because this resistance heating occurs primarily at the zone of contact between the active electrode and the tissue. The cauterization or coagulation effect is very shallow, and in some instances is thought to be too shallow to be used effectively to cauterize or desiccate highly vascular tissues of large areas, such as spleens and livers.
Where microwave energy is used in the instrument for simultaneous severing and surgically coagulating, the patient need not be grounded through a "butt plate", or other arrangement, as is normally utilized and required in conventional radio frequency scalpel techniques.
U.S. Pat. No. 4,273,127 discloses the use of a laser for cutting and coagulating tissue. A carbon dioxide laser scalpel is used to produce the coagulation, but blood loss is still excessive in incisions which involve large areas of highly vascularized tissue.
U.S. Pat. No. 3,636,943 discloses a method and apparatus for using ultrasonic energy to close off small, severed blood vessels during surgery. The ultrasonic device produces heat by means of mechanical friction to achieve the cauterization.
In U.S. Pat. No. 4,534,347 discussed above, the surgical blade which is used for resectioning is shaped to form a microwave radiating loop extending between an inner conductor and an outer or external conductor of a rigid coaxial conductor 10. The microwave scalpel is equipped with a hand switch at one end of an elongated shaft, and the surgeon can use this switch to reenergize the microwave power source during surgery.
In Wappler U.S. Pat. No. 2,002,559, a means for electrosurgically resectioning is disclosed. The device can be used for alleviating organic protrusions obstructing body cavities, and can be utilized for both resectioning and coagulating the tissue by means of suitably generated high frequency electric current. In the course of electrically resectioning a tissue, a channel or groove is cut through the tissue by the development of high frequency, high intensity current at the locus to be resectioned.
In conjunction with the electrode wire used in the resectioning and cauterizing procedure, an endoscope is provided as a part of the instrument for the purpose of completely illuminating the site of the operation. The wire electrode employed for accomplishing the resectioning can be protruded out of the shaft upon which it is mounted, so as to form a section which will engage broadside against the tissue which is to be cut. The technique further involves the use of a grounding or indifferent electrode which is made to contact the patient at some suitable point on the body. The patentee states that the type of current employed renders the cutting operation using this device entirely hemostatic, and accomplishes the resectioning in a rapid, simple manner which requires only local anesthesia.
In U.S. Pat. No. 4,506,668, a resectoscope is depicted and described which includes a high frequency cutting loop. The loop is generally U-shaped or semicircular in configuration and is mounted at the end of an extended or elongated tubular shaft. As with other high frequency cutting loops, the grounding of the patient is utilized to constitute the other terminal of the electrical circuit. The flow of current at some distance from the loop is at a harmlessly low level, but in the intermediate vicinity of the loop, the current density is highly concentrated and therefore creates a considerable rise in temperature. In this way, the loop acts to cut tissue.
Other types of electrosurgical instruments utilized for severing or cutting through tissues of the body are shown in Doane U.S. Pat. No. 1,919,543, Morrison U.S. Pat. No. 3,801,766 and Nottke U.S. Pat. No. 4,427,006. Both of the latter patents disclose electrosurgical devices having a control switch means in the instrument handle area.
The physical principles involved in electrosurgically resectioning tissues and concurrently accomplishing coagulation or cauterization are generally well understood, and have been incorporated in several different types of electrosurgical instruments. These are typified by those disclosed in the patents which have been referenced. New applications of these types of electrosurgical techniques other than those which are described in these patents await the address of persons working in this technology. One particular need has been perceived by the present inventors to reside in the field of veterinary medicine, and particularly, in the case of equine surgery employed to alleviate blockage of the air passageway and windpipe of a horse. This blockage occasionally results from an abnormal displacement of the soft palate from its normal position, in which it extends under the epiglottis and immediately above the oropharnynx, to a position in which it extends across and above the epiglottis. In the latter position, the soft palate extends across and occludes a portion of the air passageway extending the mouth and nasal passageways via the larynx to the trachea and windpipe. When this condition occurs, the animal has difficulty in breathing, and particularly when racing or running extended distances. In the latter cases, larger volumetric air intake is required in order to supply the greatly enhanced oxygen demands of the body.